1. Field of Invention
The present invention relates to a fan and in particular to a bathroom ventilator with a soft-start, low noise, power-saving and waterproof functions.
2. Related Art
The bathroom is usually equipped with the bathroom ventilator. When the user turns on the switch, the bathroom ventilator starts to generate airflows in the bathroom and thus carry the bad smell or moisture out.
However, the conventional bathroom ventilator does not have the soft-start function. Thus, once the bathroom ventilator is switched on, it will rotate at full speed within a very short time. In this case, the user can obviously hear the noise caused by the bathroom ventilator. If the noise raising rate of the bathroom ventilator reaches about 10 dB per second, the noise will make the user feel uncomfortable.
In addition, to switch on the bathroom ventilator from still state to full speed state requires a very large start-up current. Thus, the inrush current, voltage spike or spike noise may occur in the starting moment when switching on the bathroom ventilator. Moreover, the arc (electric arc phenomenon) may be generated to damage the bathroom ventilator.
Please refer to FIG. 7 which shows the conventional bathroom ventilator. The conventional bathroom ventilator is composed of a grille 10, a frame 11, an impeller 12, an AC motor 14 and a housing 15. The impeller 12 is driven by the AC motor 14. Because the conventional bathroom ventilator does not have any waterproof mechanism, the motor and its coil will be directly contaminated by dust or water to cause the dangerous voltage so that the product reliability and safety will be greatly reduced. Furthermore, the electric power for driving the conventional bathroom ventilator is usually provided by the utility power system. However, the utility power system provides the AC power supply so that the ventilator using AC motor powered by the AC power supply usually consumes relatively more energy, which leads to larger power consumption.
In addition, the impeller 12 has a base plate 12a, a hub 12b disposed on the base plate 12a, several blades 12c disposed on the base plate 12a, and a ring 12d connecting the top portions of the blades 12c. However, due to the small number of blades, the performance of air intake will be affected and the noise of airflow is loud. The noise mainly comes from the electrical noise of motor, vibration and airflow, wherein the noise of airflow is the major source.